grpc+protobuf 的C++ service 实例解析

这篇文章将会简单的描述一下grpc+protobuf 的C++ service的搭建过程，告诉读者在linux系统下怎样实现一个service接口的流程。

一、.proto文件的

实现一个简单的helloworld回显功能，首先需要一个.proto文件，我将它命名为example.proto，文件内容如下：

	syntax = "proto3";

	message SearchRequest
	{
		string Request = 1;
	}

	message SearchResponse
	{
		string Response = 2;
	}

	service SearchService {
  		rpc Search (SearchRequest) returns (SearchResponse);
	}

二、自动生成代码

使用example.proto文件自动生成grpc和protobuf的代码

protoc --cpp_out=./ examples.proto
protoc --grpc_out=./ --plugin=protoc-gen-grpc=/usr/local/bin/grpc_cpp_plugin examples.proto

这两个命令将会生成四个文件， examples.grpc.pb.cc、examples.grpc.pb.h、examples.pb.cc、examples.pb.h。

三、服务器代码

#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 

#include "examples.grpc.pb.h"

using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;

class SearchRequestImpl final : public SearchService::Service {
  Status Search(ServerContext* context, const SearchRequest* request,
                  SearchResponse* reply) override {
    std::string prefix("Hello ");
    reply->set_response(prefix + request->request());
    return Status::OK;
  }
};

void RunServer() {
  std::string server_address("0.0.0.0:50051");
  SearchRequestImpl service;

  ServerBuilder builder;
  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
  builder.RegisterService(&service);
  std::unique_ptr server(builder.BuildAndStart());
  std::cout << "Server listening on " << server_address << std::endl;

  server->Wait();
}

int main(int argc, char** argv) {
  RunServer();

  return 0;
}

四、客户端代码

#include 
#include 
#include 

#include 
#include 

#include "examples.grpc.pb.h"

using grpc::Channel;
using grpc::ClientAsyncResponseReader;
using grpc::ClientContext;
using grpc::CompletionQueue;
using grpc::Status;


class ExampleClient {
 public:
  explicit ExampleClient(std::shared_ptr channel)
      : stub_(SearchService::NewStub(channel)) {}
 
  std::string Search(const std::string& user) {
 
    SearchRequest request;
    request.set_request(user);
 
    SearchResponse reply;
   
    ClientContext context;

    CompletionQueue cq;

    Status status;

    std::unique_ptr > rpc(
        stub_->AsyncSearch(&context, request, &cq));

    rpc->Finish(&reply, &status, (void*)1);
    void* got_tag;
    bool ok = false;
  
    GPR_ASSERT(cq.Next(&got_tag, &ok));

   
    GPR_ASSERT(got_tag == (void*)1);
  
    GPR_ASSERT(ok);

    if (status.ok()) {
      return reply.response();
    } else {
      return "RPC failed";
    }
  }

 private:
 
  std::unique_ptr stub_;
};

int main(int argc, char** argv) {
  ExampleClient client(grpc::CreateChannel(
      "localhost:50051", grpc::InsecureChannelCredentials()));
  std::string user("world");
  std::string reply = client.Search(user);  // The actual RPC call!
  std::cout << "client received: " << reply << std::endl;

  return 0;
}

五、Makefile文件

subdir = ./

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig

SOURCES = $(wildcard $(subdir)*.cc)
SRCOBJS = $(patsubst %.cc,%.o,$(SOURCES))
CC = g++

%.o:%.cc
	$(CC) -std=c++11 -I/usr/local/include -pthread -c $< -o $@

all: client server

client:	examples.grpc.pb.o examples.pb.o examples_client.o
	$(CC) $^ -L/usr/local/lib `pkg-config --libs grpc++ grpc` -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed -lprotobuf -lpthread -ldl -lssl -o $@

server:	examples.grpc.pb.o examples.pb.o examples_server.o
	$(CC) $^ -L/usr/local/lib `pkg-config --libs grpc++ grpc` -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed -lprotobuf -lpthread -ldl -lssl -o $@
#chmod 777 $@

clean:
	sudo rm *.o

六、运行

运行./server启动service，在另一个端口运行./client 打印出：client received: Hello world表示两边已通，grpc+protobuf 搭建完成。